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  • Irish Chronicles Document Links Between Volcanoes and Weather
    A study of over 40,000 written entries in Irish Annals and ice core measurements shows a strong corr...Read more

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    Irish Chronicles Document Links Between Volcanoes and Weather

    A study of over 40,000 written entries in Irish Annals and ice core measurements shows a strong correlation between the occurrence of volcanic eruptions and extreme cold weather in Ireland over a 1200 year period. Data analyzed in this study cover the period from 431 to 1649, during which time up to 48 volcanic eruptions are identified in Greenland ice core records through deposition of volcanic sulfate in annual layers of ice. You can find the study (open access), published on 6 June 2013 in IOP Publishing's journal Environmental Research Letters, at http://iopscience.iop.org/1748-9326/8/2/024035/article. Find out more about how volcanoes can influence climate.
  • EF-5 Tornado in El Reno, Oklahoma Widest Ever Recorded in US
    The EF-5 tornado that hit El Reno, Oklahoma on May 31st was the widest ever recorded in the US, acco...Read more

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    EF-5 Tornado in El Reno, Oklahoma Widest Ever Recorded in US

    The EF-5 tornado that hit El Reno, Oklahoma on May 31st was the widest ever recorded in the US, according to the National Weather Service in Norman Oklahoma. The tornado, which remained on the ground for 40 minutes and reached 2.6 miles across (4.2 km), took the lives of 18 people including storm chasers Tim Samaras, Paul Samaras and Carl Young. For more information on the tornado, visit http://ow.ly/i/2hfDG.
  • Atmospheric CO2 Level Tops 400 ppm
    During the week of May 13th, the CO2 level at the Mauna Loa Observatory in Hawaii topped 400 ppm rep...Read more

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    Atmospheric CO2 Level Tops 400 ppm

    During the week of May 13th, the CO2 level at the Mauna Loa Observatory in Hawaii topped 400 ppm repeatedly. Daily levels of CO2 can vary due to weather, and there are seasonal trends as well. The level of atmospheric greenhouse gases continues to increase, now over 120 ppm since the Industrial Revolution began. For more on the Keeling Curve, see http://keelingcurve.ucsd.edu/. Find out more about greenhouse gases and warming.
There are two types of electrical currents: direct current (DC) and alternating current (AC). Direct current flows in a single direction along wires. Alternating current flows back and forth, rapidly switching direction many times per second.
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Direct Current (DC) & Alternating Current (AC) Electricity

There are two types of electrical currents that can flow through wires: direct current (DC) and alternating current (AC).

Direct current (DC) electricity flows in the same direction all the time through an electric circuit. The electrons that carry the electricity in a wire mostly move in one direction in a DC circuit. A flashlight with its batteries, bulb, and wires is a common example of a DC circuit.

The outlets in our homes provide alternating current (AC) electricity. The flow of electrons in an AC circuit switches direction very quickly - 60 times every second! The electrons first flow one way, then the other. However, the electrical devices we use don't care which direction the electrons are moving, since the same amount of current flows through a circuit regardless of the direction of the current.

Electric power distribution networks which deliver electricity to our homes are set up to handle alternating current electricity. Space weather storms can cause flows of direct current electricity in the electrical power grid. Since the grid was designed to used AC electricity but not DC electricity, the space weather induced direct currents can damage or destroy some types of equipment, such as voltage transformers.

Last modified February 17, 2009 by Randy Russell.

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